The pitcher plants in Canada don’t just eat insects – they also feast on amphibians. A survey late last summer revealed that a fifth of the pitchers in one bog had caught at least one juvenile salamander.
“That was a WTF moment,” says Alex Smith of the University of Guelph.
Pitcher plants are famous for feeding on insects. But last year, Smith found a young yellow spotted salamander trapped in one of the pitchers of the purple pitcher plant (Sarracenia purpurea purpurea) while doing field work with undergraduates at Algonquin Provincial Park in Ontario.
He mentioned it to Patrick Moldowan of the University of Toronto and other researchers. They started looking out for trapped salamanders and soon made further discoveries.
In August and September, Moldowan did a survey, checking the contents of more than 100 plants on several occasions. In late August and mid-September – the time when thousands of newly metamorphosed salamanders emerge en masse from a nearby lake – he found a fifth of plants had caught at least one salamander.
It’s not clear whether this site is exceptional. But it’s a well studied site, says Smith, so it might just be that no one has realised how common this before.
For those salamanders that cannot escape, it’s a slow death. It takes between three and 19 days for them to die. What kills them is not known – they might starve to death, overheat as the pitchers warm in the sun or be killed by something in the fluid.
Overall, the team estimates that up to 5 per cent of the emerging salamanders may be killed by the pitchers – making the pitchers a major predator.
For the pitchers, the young salamanders could be a substantial source of food, as they are much larger than the plants’ usual invertebrate prey. The team plan to do further studies to confirm the plants are feeding on them, and are not overwhelmed by the glut of nutrients.
Some tropical pitchers of the genus Nepenthes rely on vertebrates such as tree shrews and bats – but they don’t eat them. Instead, they act as a toilet, feeding on the faeces of these animals.
There have been reports of large Nepenthes catching “rats”, but these are likely to be unlucky tree shrews that slipped while using the facilities, rather than the plants’ regular diet.
Journal reference: The Scientific Naturalist, DOI: /10.1002/ecy.2770
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